Page "History of Thailand" Paragraph 21

The overpopulation might have encouraged the Tais to seek their fortune further southwards.

By 1100 AD, the Tai had established themselves as Po Khuns ( ruling fathers ) at Nan, Phrae, Songkwae, Sawankhalok, Chakangrao, etc.

on the upper Chao Phraya valley.

These southern Tai princes faced Khmer influence from Lavo.

Some of them became subordinates to the Lavo-Khmer polity.